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For example, "debugging mode" will tell Blackfire to disable pruning - that's when it removes data for functions that don't take a lot of resources - and also to disable anonymization - that's when it hides exact details used in SQL queries and HTTP requests. Debugging mode is nice if something weird is going on.. and you want to fully see what's happening inside a request.

Another superpower of Blackfire is called distributed profiling... which you either won't care about... or it's the most awesome thing ever. Imagine you have a micro-service architecture where, when you load the page, it makes a few HTTP requests to some microservices. If you have Blackfire installed on all of your microservices, Blackfire will automatically create profiles for every request made to every app. The final result is a profile with sub-profiles that show you how the entire infrastructure is working together. It's... pretty incredible.

But, if you want to disable it and only profile this main app, you can do that with this option.

But what I really want to look at is this "Profile all requests" link. Hit "Record"... then refresh. Woh! Cool! It already made 2 requests! And if I scroll down a little bit... there's a third! Let's stop right there.

That jumps us to our Blackfire dashboard. These last three profiles were just created: one for the homepage and two others: these are both AJAX calls! Surprise! Without even thinking about it, we discovered a few extra requests that are part of that page.

This first one - /api/github-organization - is what loads this GitHub repository info on the right. This makes an API call for the most popular repositories under the Symfonycasts organization... which is kind of silly... but it was a great way to show how network requests look in Blackfire. We'll see that in a minute.

This other request - for /_sightings - is an AJAX call that powers the forever scroll on the page.

Basically... I like using "profile all requests" in 3 situations. One, to get an idea of what's all happening on a page. Two, to profile AJAX requests... though I'll show you another way to do that soon. And three, to profile form submits: fill out the form, hit "Record", then submit.

Let's look closer at the /api/github-organization AJAX profile: https://bit.ly/sf-bf-github-org. As I mentioned, this makes a network request to the GitHub API to load repository information. The profile... is almost comical! Out of the 438 millisecond wall time - 82% of it is from curl_multi_select() - that's the time spent making any API calls.

It's kind of fun to look at this in the CPU dimension, which is only 74 milliseconds. curl_multi_exec() is still the biggest offender... but it's a lot less obvious what the critical path is. Compare that with the I/O wait dimension, which includes network time. The critical path is ridiculously obvious here. This is an extreme example of how different dimensions can be more or less useful depending on the situation.

One of the interesting things is that... this is not the full call graph. According to this, the code goes straight from handleRaw() - which is the first call into the Symfony Framework - to our controller. In reality, there are many more function calls in between. Switch back to the CPU dimension. Yep! This shows more nodes.

This is the result of that "pruning" I mentioned a few minutes ago. Blackfire removes function calls that don't consume any significant resources so that the critical path - from a performance standpoint - is more obvious. The call graph also automatically hides or shows some info based on what you're zoomed in on.

In this situation, the critical path is obvious. You can also see the network requests on top. There are actually two: one that returns 1.5 kilobytes and another that returns 5.

This shows the network time too... but at least if you're using the Symfony HTTP client like I am, these numbers aren't right - they're far too small... I think that's due to the asynchronous nature of Symfony's HTTP Client. That's ok - because the overall cost is showing up correctly in all the other dimensions.

So how do we fix this? Should we add some caching? Or somehow try to make only one API call instead of two? We're actually going to revisit and fix this problem later. For now, I wanted you to be aware of the "Profile All" feature. Next, let's check out the Blackfire command-line tool, which has two superpowers... one of which has nothing to do with the command line.